This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Obesity in the United States is reaching epic proportions with 65% of the population being defined as overweight (body mass index-BMI>25) and 30% also qualifying as obese (BMI>30). Obesity is linked to numerous adverse health consequences including cardiovascular disease, diabetes and cancers of the colon, prostate, pancreas, breast and endometrium (uterine lining). Endometrial cancer is the fourth most common cancer in women in the United States and is expected to affect 40,000 women in 2005. Approximately 40% of endometrial cancer may be attributed to obesity and this is thought to be primarily due to the increased estrogen production in adipocytes (fat cells) through the conversion of androgens to estrogens. Yet not all obese women will develop endometrial cancer suggesting that other factors aside from the increased estrogen must also play a role in the process of malignant transformation. Protective factors in obese women include physical activity but the exact mechanisms that underlie such protection remain poorly understood. Little prospective data exist on adipocyte derived factors or physical activity levels in overweight and obese women. Therefore, the purpose of this study is prospectively collect baseline physical activity measures, baseline body mass index, baseline hormonal levels, blood/fat samples, and endometrial samples from overweight and obese postmenopausal women who are undergoing hysterectomy. After collection, we will explore and identify differences in either fat or blood biomarkers or in physical activity levels in women with and without endometrial cancer. The goal of this research is to better define risk factors in postmenopausal overweight and obese women that predispose to endometrial cancer and to identify any protective factors that correlate with physical activity. The ultimate goal of the research is to be able to predict, and perhaps to eventually prevent, the development of endometrial cancer in obese women.